ios - Thread 1:EXC_BAD_INSTRUCTION error when calling "addObjectsFromArray"method for NSMutableArray -

i have created program calculates borders of countries based on custom object being inputed function. function returns array of custom objects. keep getting error when trying add array nsmutablearray. error called "thread 1: exc_bad_instruction(code=exc_1386_invop, subcode=0x0)".

here adding code:

@iboutlet var label: uilabel! @iboutlet var imageview: uiimageview!  override func viewdidload() {     //afganistan      afghanistan.name = "afghanistan"     afghanistan.borders.addobjectsfromarray(relate(afghanistan))      label.text = string((afghanistan.borders[0] as! develop).name)  } 

here relate method along group dictionary:

func relate(x : develop) -> array<develop>{  var : [develop] = []    (_, value) in groups {      y in value {          if y.name == x.name {              in value {                  if i.name != x.name {                     a.append(i)                 }              }          }            }     }     return  }  //groups var groups = [      "one": [afghanistan]  ] 

here class of develop:

    class develop : nsobject, nscoding {  //shared      var power : int!     var name : string!     var image : uiimage!     var flag : uiimage!     var militaryname : string!  //military      var experience : int!     var oatc : int!     var navy : int!     var airforce : int!     var artillery : int!   //geography      var borders : nsmutablearray!     var cities : nsmutablearray!     //biomes     var biom : nsmutablearray!      var continent : string!     var nsew : string!       //encoding section   required convenience init(coder decoder: nscoder) {     self.init()     //shared     self.power = decoder.decodeobjectforkey("power") as! int     self.name = decoder.decodeobjectforkey("name") as! string     self.image = decoder.decodeobjectforkey("image") as! uiimage     self.flag = decoder.decodeobjectforkey("flag") as! uiimage     self.militaryname = decoder.decodeobjectforkey("militaryname") as! string      //military     self.experience = decoder.decodeobjectforkey("experience") as! int     self.oatc = decoder.decodeobjectforkey("oatc") as! int     self.navy = decoder.decodeobjectforkey("navy") as! int     self.airforce = decoder.decodeobjectforkey("airforce") as! int     self.artillery = decoder.decodeobjectforkey("artillery") as! int      //geography     self.borders = decoder.decodeobjectforkey("borders") as! nsmutablearray     self.cities = decoder.decodeobjectforkey("cities") as! nsmutablearray      self.continent = decoder.decodeobjectforkey("continent") as! string     self.nsew = decoder.decodeobjectforkey("nsew") as! string  }  convenience init(     power: int, name: string, image: uiimage, flag: uiimage,     relations: nsmutablearray, mname: string, experience: int,     oatc: int, navy: int, airforce: int, artillery: int,     borders: nsmutablearray, cities: nsmutablearray,     biom: nsmutablearray, continent: string, nsew: string ) {     self.init()     //shared     self.power = power     self.name = name     self.image = image     self.flag = flag     self.militaryname = mname     //military     self.experience = experience     self.oatc = oatc     self.navy = navy     self.airforce = airforce     self.artillery = artillery     //geography     self.borders = borders     self.cities = cities     self.biom = biom     self.continent = continent     self.nsew = nsew }  func encodewithcoder(coder: nscoder) {     //shared     if let power = power { coder.encodeobject(power, forkey: "power") }     if let name = name { coder.encodeobject(name, forkey: "name") }     if let image = image { coder.encodeobject(image, forkey: "image") }     if let flag = flag { coder.encodeobject(flag, forkey: "flag") }     if let militaryname = militaryname { coder.encodeobject(militaryname, forkey: "militaryname") }     //military     if let experience = experience { coder.encodeobject(experience, forkey: "experience") }     if let oatc = oatc { coder.encodeobject(oatc, forkey: "oatc") }     if let navy = navy { coder.encodeobject(navy, forkey: "navy") }     if let airforce = airforce { coder.encodeobject(airforce, forkey: "airforce") }     if let artillery = artillery { coder.encodeobject(artillery, forkey: "artillery") }     //geography     if let borders = borders { coder.encodeobject(borders, forkey: "borders") }     if let cities = cities { coder.encodeobject(cities, forkey: "cities") }     if let biom = biom { coder.encodeobject(biom, forkey: "biom") }     if let continent = continent { coder.encodeobject(continent, forkey: "continent") }     if let nsew = nsew { coder.encodeobject(nsew, forkey: "nsew") } } } 

"afghanistan" subclass of develop